STPMIC1APQR datasheet(42/140 Pages) STMICROELECTRONICS

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Enable/disable – PWR_USB_SW can be enabled in POWER_ON state by I2C setting of VBUSOTG_ON bit

in Table 48. BST_SW_CR register. PWR_USB_SW switch cannot be enabled automatically during power-up

sequence. During power-down sequence, switch is turned OFF in RANK0 phase.

It is recommended that PWR_USB_SW is enabled only after boost converter works in steady-state (after boost

start-up sequence). This is typically ~2 ms after boost is enabled. Nevertheless, if PWR_USB_SW is enabled

earlier than Boost, it turns ON only when both boost is enabled by BST_ON bit and BSTOUT voltage is higher

than ~VIN.

Boost OVP – When boost OVP is detected PWR_USB_SW is disabled automatically.

VBUSOTG pin monitoring – When PWR_USB_SW is OFF, VBUSOTG voltage is monitored by VBUSOTG det.

to detect VBUS voltage rising/falling from USB OTG connector due to USB cable insertion/removal.

When voltage on VVBUSOTG pin goes higher than VVBUSOTG_Rise threshold, the interrupt and/or turn-ON condition

is generated. When voltage on VBUSOTG pin goes below than VVBUSOTG_Fall threshold, the interrupt is

generated. VBUSOTG pin monitoring is filtered by tVBUSOTGDB debounce timer for both rising and falling

voltage. VBUSOTG detector is enabled by default and can be disabled by setting VBUSOTG_DET_DIS bit

Table 48. BST_SW_CR register.

Soft-on/off –Switch implements soft-on, soft-off circuit. After the switch is enabled, switch starts operating in

“current limiting” mode, gradually increasing the output current limit until the switch is fully turned ON. This soft-on

phase has a duration defined by tSS_VBUSOTG.

The same mechanism is also applied during switch soft-off phase during turn-off to prevent quick unloading of

BSTOUT and excessive voltage overshoot.

Overcurrent limitation – Switch implements 2 levels of overcurrent protection:

When load on the output exceeds overcurrent limit threshold IVBUSOTGOCP, switch starts limiting the output

voltage to decrease output current. If the switch stays in this condition for more than tOCPDBSW, switch is

automatically turned OFF, and VBUSOTG_OCP interrupt generated.

In case the output load exceeds IVBUSOTG_SH threshold, switch turns OFF immediately to prevent

boost overload, and VBUSOTG_SH interrupt is generated. Shortly after this action, switch is re-enabled

automatically with standard soft-on current limiting procedure. In case the overload condition is still present,

the switch continues operation in current limiting mode, and is finally switched OFF after tOCPDBSW. In case

overload condition is removed before tOCPDBSW, switch continues its normal operation.

For detailed behavior of the device on OCP event refer to Section 5.4.7 Overcurrent protection (OCP).

Output discharge – Switch implements passive discharge circuit (by default disabled) that can be enabled by

setting VBUSOTG_PD bit in Table 48. BST_SW_CR.

PWR_SW is a configurable 500 mA/1000 mA power switch that can be used to power supply one or two USB

host ports or for general purpose.

It has dedicated the input SWIN and the output SWOUT pin.

Minimum SWIN voltage to enable the switch is VSWIN_Rise.

PWR_SW pin is a switch without reverse current protection. If voltage on SWOUT is higher than SWIN-0.7 V, a

leakage from SWOUT to SWIN occurs even if the switch is OFF.

Enable/disable – PWR_SW can be enabled in POWER_ON state by I2C setting of SWOUT_ON bit in

Table 48. BST_SW_CR. PWR_SW switch cannot be enabled automatically during power-up sequence. During

power-down sequence, switch is automatically turned OFF in RANK0 phase.

PWR_SW turns ON only when SWIN voltage is higher than VSWIN_Rise threshold.

If the switch is supplied by boost, it is recommended to enable the switch after boost is already in steady-state

with 5.2 V output. This is typically ~2 ms after boost is enabled.

Boost OVP – When boost OVP is detected, switch is ON by default. It is disabled automatically only if

NVM_SWOUT_BOOST_OVP bit is set.

SWOUT pin monitoring – When PWR_SW is OFF, SWOUT voltage is monitored by SWOUT detector.

When VSWOUT > VSWOUT_Rise, interrupt and turn-ON condition is generated. SWOUT detector is enabled by

default and can be disabled by setting SWOUT_DET_DIS bit in Table 30. SW_VIN_CR.

tSWOUTDB debounce timer is on SWOUT detector output.

SWIN pin monitoring – SWIN detector is disabled by default and can be enabled to monitor the voltage on SWIN

pin by setting SWIN_DET_EN bit in Table 48. BST_SW_CR.

When VSWIN > VSWIN_Rise, interrupt is generated.

STPMIC1

Boost converter and power switches

DS12792 - Rev 7

page 42/140

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